Radiation therapy is the medical use of high doses of ionizing radiation and typically used in the treatment of cancer to kill malignant cells. Radiation therapy can be used as a primary treatment or used in conjunction with other treatments, such as chemotherapy or surgery. In addition to cancerous cells, radiation therapy can damage healthy cells, making it imperative that treatment is carefully planned to minimize side effects. The type of radiation treatment given to cancer patients is dependent on many factors, including the type of cancer, stages of cancer, and the location of the cancer within the body.
Radiation therapy is used to treat many types of cancer, including: breast, bladder, vaginal, uterine, ovarian colon, rectal, kidney, lung, prostate, and thyroid cancers. Each type of cancer has specific treatment options. For example, in bladder cancer, radiation treatment typically involves the use of Intensity-Modulated Radiation Therapy (IMRT) that utilizes a computer-controlled linear accelerator. In IMRT, the beam from the linear accelerator is focused on a predetermined location based on a three-dimensional shape of the tumor acquired through computer tomography (CT) or magnetic resonance images (MRI). The three-dimensional image is made prior to beginning treatment. Small marks on the skin are made along the treatment area, pinpointing the telemetry of the beam so as not to damage healthy cells.
However, some tumors do not have a consistent, precise position because of the nature and location of the cancer in the internal organs. For example, radiation therapy for patients with bladder cancer is difficult due to the anatomy of the bladder. The bladder is an elastic organ, which frequently contracts and expands with urine. Organ motion and deformation (change in shape) prevent the accurate localization of the radiation beam to the tumor and as a result exposes normal healthy organs to unnecessary radiation. Therefore, the three-dimensional image acquired prior to starting a radiation therapy plan may not be useful for subsequent radiation appointments if, in comparison to when the image was produced, the bladder has expanded or deflated with urine. Consequently, if the beam is not in the precise position, it could cause damage to healthy cells.
There are approximately 75,000 new cases of bladder cancer per year in the United States. In the majority of cases, surgery is used to treat patients with bladder cancer by surgically removing all or part of the bladder (cystectomy). This is especially true for patients with muscle invasive transitional-cell carcinoma of the bladder, where the cancer invades the muscular layer of the bladder wall. As a replacement for the full or partial removal of the bladder, the bladder is reconstructed from portions of the bowel. This is a major surgery with significant impact of a patients' quality of life due to incontinence. Alternatively, radiation and chemotherapy are used together to treat bladder cancer to avoid this particular surgery, called bladder-preservation therapy. Bladder preservation is essential to the quality of life of patients, and there has been an effort among the medical community to preserve the bladder in patients being treated for bladder cancer.
Clinical studies show that bladder patients undergoing chemo-radiation therapy have about a 50% survival rate (similar to surgery); however, about 20-30% of these patients surviving the chemo-radiation treatment have significant radiation damage to their bladder making it useless (incontinence). This serious side effect is due to the unnecessary exposure of the normal bladder to high doses of radiation during radiation treatment as a result of the change in shape and size of the bladder during the radiation treatment. The exposure to radiation typically last about 30 minutes per day, 5 days per week, for about 7 weeks. Due to the inaccurate delivery of radiation during bladder cancer treatment and its negative side effects, the radiation dosage delivered to the bladder tumor cannot be given as high as needed. The typical current dose of radiation to bladder tumors is about 6,300 to 6,500 rads (a “rad” is a unit of radiation treatment dosage), instead of the needed dose in the range of 7,000-8,000 rads for solid tumors. Any advancement in the precision of radiation treatment would increase the chances of having a safe and effective alternative to cystectomy.
One development towards addressing organ movement and its relation to radiation treatment has been the use of Image-Guided Radiation Therapy (IGRT). IGRT uses radiograph images in conjunction with a linear accelerator to improve the accuracy of daily targeting of the tumor. In IGRT the linear accelerator uses image technology (X-ray, CT scan) to take frequent images immediately prior to, and sometimes during treatment. This technology has been used in many cancers including bladder cancer. Although the use of this technology would improve chances of bladder preservation, it is still difficult to immobilize the bladder during the radiation treatment to limit organ movement and deformation. Moreover, it is also difficult to place markers within the bladder as a guide for radiation treatment without the use of invasive surgery.
There are currently devices that affect the shape of the bladder by continually draining urine. A Foley catheter may be used to continually drain urine from the body using a balloon and multiple lumina. One lumen drains urine from the bladder and another lumen fills the balloon with sterile water in order to prevent the balloon from slipping out of the bladder. However, the Foley catheter is primarily used for irrigation of the bladder and it is not designed to maintain the bladder in a constant shape and volume. The Foley catheter balloon is much smaller than the interior of the bladder and thus cannot control the expansion or contraction of the bladder. In addition, a Foley catheter is typically used as a more permanent solution to incontinence.
In light of the above, it would be advantageous to provide a means of reducing the exposure of healthy cells to harmful radiation. It would be further advantageous to provide an apparatus to immobilize the bladder or other elastic organ to retain its shape during radiation treatment to prevent damage to healthy cells and to minimize side effects. It would be further advantageous to provide an apparatus having stationary markets able to be removably inserted into the bladder or other elastic organ to guide any radiation treatment to the correct area of the tumor without the need for invasive surgery. By knowing the exact position of the tumor and surrounding critical organs, one can improve the treatment outcomes by increasing the dose of radiation to the tumor (hence, higher cure rate) and reducing the dose of radiation to the surrounding critical organs (less side effects and complications). Having this immobilization device will enhance the therapeutic windows of the treatment, i.e., increasing the cure rate and reducing the side effects of the treatment.